Child Having Sore Throat, Headache, Viral Infection. Hurt Arm While Taking Blood Sample, Constant Pain. Nerve Damage?

Good evening, I hope you can help...my ten year old daughter has been unwell for four weeks now...started off as flu like symtoms, sore throat , headache, runny nose ...then changed to her being breathless and lethargic...took her to our GP who diagnosed her with a viral infection, and recommended bed rest and lots of fluids...however, four weeks in, and her condition hasn t improved and to add to her woes, when the hospital attempted to take a blood sample they have hurt her arm and nearly a week on she can barely move it and it gives her constant pain...could this be nerve damage? Will this ease? Should I be worried that after four weeks there are no dramatic nor slight signs of improvement? Many thanks